It is known that chelating agents such as ethylenediaminetetraacetic acid (EDTA), when chelated with a radionuclide, can be used in organ imaging. However, the complex of EDTA and a radionuclide is of limited use in certain organs where lipo-solubility is necessary.
It is known that fluorescent groups such as fluorescein isothiocyanate can be introduced into biological or clinical compounds of interest. Analytical techniques employing fluorescein frequently lack the requisite sensitivity for the detection and measurement of nanomolar or picomolar levels of organic substrates. The lack in sensitivity of techniques which employ fluorescein is believed to be due to the high fluorescence background of biological fluids and to fluorescein's high degree of overlap in fluorescent excitation and emission spectra.
It is an object of the present invention to provide carbamate compounds of 2-ureado-6-hydroxypyridine which are strong chelating agents suitable for forming stable chelates, particularly with the rare earths, transition metals and radionuclides.
It is also an object of the present invention to provide novel bi-functional carbamates of 2-ureado-6-hydroxypyridine which may be readily coupled to compounds of clinical or biological interest to provide derivatives which form stable complexes with suitable metal ions and which exhibit radioactivity or fluorescence. An object of this invention is to provide radioisotopic labeled compounds which exhibit rapid preferential location in animals regardless of liposolubility. It is a further object of the invention to provide fluorescent labeled compounds which circumvent the overlap of the excitation and emission spectra of known compounds and which exhibit limited background fluorescence. A further object of this invention is to provide novel chelates which will exhibit distinct fluorescence excitation and emission spectra corresponding to that of the specific metal ion which is chelated, which chelates are stable and not deleterious to the biological compounds of interest. Yet another object of this invention lies in the coupling of the novel moieties to form adducts with a broad spectra of biological and clinical compounds by facile and gentle chemical reactions.